title: Coherent ultrasonic Doppler tomography.
abstract: Ultrasonic imaging based on the pulse-echo principle is widely used throughout the world, particularly in medical applications. However, its spatial resolution is poor (around 2 times the wavelength, or 200 μm at 15 MHz), limiting its ability to detect small but clinically important lesions (such as microcalcifications in breast cancer). The work presented here is different from the traditional approach. Continuous-wave ultrasound is transmitted to insonate a rotating object, then the amplitude and phase of the returned signals are coherently processed to reconstruct a Doppler tomographic image of the object's backscatter field. It is demonstrated numerically that the spatial resolution is up to 0.19 wavelengths and the sampling requirement and image formation method are given. To show the performance of the method, we present the results obtained by applying the new technique in simulation and experiment. A string phantom consisting of very thin copper wires and two cylindrical phantoms constructed by tissue-mimicking-material were scanned. It is demonstrated that the copper wires were located very accurately with very high spatial resolution, and good shape approximation for the cylindrical phantoms was achieved.
authors.affiliation: Department of Medical Physics and Bioengineering, University Hospitals Bristol NHS Foundation Trust, Bristol General Hospital, Bristol, UK. chun_sing_tsui@hotmail.com
authors.forename: Chun Sing Louis
authors.initials: CS
authors.lastname: Tsui
authors.forename: Hai-Dong
authors.initials: HD
authors.lastname: Liang
authors.forename: Michael
authors.initials: M
authors.lastname: Halliwell
authors.forename: Mike
authors.initials: M
authors.lastname: Shere
authors.forename: Jeremy P
authors.initials: JP
authors.lastname: Braybrooke
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Whipp
authors.forename: Peter N T
authors.initials: PN
authors.lastname: Wells
mesh_terms: D000465:Algorithms; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D041623:Tomography, Optical Coherence / Q000295:instrumentation / Q000379:methods*; D018608:Ultrasonography, Doppler / Q000295:instrumentation / Q000379:methods*